A pre- or postharvest foliar B application was found to increase fruit set of ‘Italian’ prune (Prunus domestica L.). A prebloom B spray failed to increase set. Neither fall nor spring applications influenced the amount of fruit lost in the midsummer or “blue” drop. All trees involved in the experiment had adequate B by the standard index of tree nutrition, August mid-shoot leaf analysis. Incipient B deficiency did not appear to be involved. Fall foliar B increased B levels in dormant bud and spur tissues and in flower buds and flowers. A prebloom B spray increased B levels of floral tissues to a lesser degree. The highest B concentration was found in the ovary. Boron concentration in flower buds in April following a fall B spray was as much as five times the amount found in mid-shoot leaves in August. August mid-shoot leaf analysis revealed higher levels in leaves from trees treated the previous fall in only one of the 2 years. Several morphological and physiological effects of the fall B spray were observed. Among these were a slight delay in the time of bud break, a decrease in the size of flower buds and mature flowers accompanied by reduction of style and pedicel length, and a decrease in pollen germinability. B level of pistil and pollen had no effect on in vivo pollen tube growth rate.

Intact lamina (leaf blade) of young leaves from red-fruited pears were analyzed by fourth derivative attenuance (~absorption) spectroscopy. This method was used to extend electrophoresis based identification procedures. When the two methods were used in combination before fruit development, red-fruited pears were distinguished from the non-red-fruited parent cultivars, and these from other red-fruited and non-red-fruited pear cultivars.

Single crystals and clusters of crystals or druses found by polarized light microscopy in tissues of Pyrus malus L. cv. Jonathan were found to contain Ca using the electron microprobe. Crystals insoluble in 20% acetic acid occurred in cells adjacent to the vascular tissues near the pedicel in mature fruit and in dormant flower buds, stems, petioles, shoot apex, roots and callus tissue. Because of deposition of calcium as crystals, calcium supplies to cortical cells of apple fruit may be limited and may result in an increased incidence of internal breakdown due to low Ca levels in those cells.

Apple (Pyrus malus L.) seedlings or rooted layers growing in nutrient solution in the greenhouse were used to determine the role of xylem and phloem in the accumulation of Ca in the leaves. 45calcium accumulation increased with increasing rates of transpiration as measured by water losses. Girdling experiments demonstrated that the phloem was the primary route of translocation. Young leaves accumulated more 45ca than old leaves even though the water losses for plants bearing only young leaves or only old leaves were similar. 45calcium accumulation in mature leaves was decreased when the shoot tips were removed. Apparently, in young apple trees Ca moves primarily in the phloem, but leaks into the xylem at increasing reates in the younger stem and near the growing apex.